Process for the manufacture of alpha,alpha-dialkyl-upsilon-cyanobutyric acids

ABSTRACT

OXIDATION OF A,A-DIALKYL-Y-CYANOBUTYRALDEHYDES TO THEIR CORRESPONDING CARBOXYLIC ACIDS USING BORIC OR TITANIC ACID ESTERS AS CATALYSTS.

United States Patent 3,553,247 PROCESS FOR THE MANUFACTURE OF 11,0:- DIALKYL y-CYANOBUTYRIC ACIDS Helmut aus der Fiinten, Mondorf, and Hermann Richtzen- 3,553,247 Patented Jan. 5, 1971 butyric acids by the oxidation of a,ot-dialkyl-'y-cyanobutyraldehydes is carried out in an acid or neutral medium with oxygen or oxygen-containing gases as the oxidizing agents, in inert solvents and under pressure if desired. The catalysts are esters of boric acid and/or titanic acid hain, Schwellenbach, Post Marialinden, Germany, as- 5 signors t Dynamit N b l AG, T i d -f, B i k which are preferably used in quantities of 0.1 to of .Cologne, Cermany the weight of the aldehyde being oxidized. a g Flled P 1967, 683,353 The oxidation is best performed between 10 and Claims P y, appllcatlon y, 1966, 200 C., and preferably between 20 and 100 C. It can D 51,762 be done at normal pressure or at elevated pressure. Ali- Int Cl C07c 121/00 10 Us Cl 260 465 4 8 Claims phatic, cycloaliphatic or aromatic hydrocarbons and carboxylic acids and their esters are suitable as solvents.

Suitable exemplary solvents include benzene, toluene, xy- ABSTRACT OF THE DISCLOSURE lene, hexane, heptane, cyclohexane, acetic acid, butyric 15 acid, etc. It is preferred to employ the acid being prooxldation of a,a-diallfyl-v:cyanobutyraldehydes to t duced as the solevnt since this facilitates product recovery. corresponding carboxylic acids using bone or titanic acid Alkyl esters having alkyl groups f up to about 6 Carbon esters as catalystsatoms are preferred for use as catalysts. These are exemplified by methyl esters, isopropyl esters and butyl esters. The presentm'ventlon relates ap e forthe a The oxidation can be performed with the following fflcture 0f e y -vy y fields y the OXldaot,oc-1OW6I alkyl substituted aldehydes for example: tion of aldehydes of the general formula a,ot-dimethyly-cyanobutyraldehyde, or,-diethyl-y-cyanobutyraldehyde, NC-CH2'-CH2"CHO ot-methyl-ot-n-propyl-'y-cyanobutyraldehyde,

a,ot-dipropyl-y-cyanobutyraldehyde, l a-ethylot-butyl-v-cyanobuyraldehyde, wherein R and R each represents an aliphatic radical OPpentybvcyanobuymldemde, and R can be the same or different. em anobut raldeh de or It is in the prior art to oxidize aldehydes with oxygen y 7 y y y 0L,oL-dlhCXYL'YCYElIlObUIS/IZildGhYdfi. oxygen-containing gases in an acid or neutral medium, or other oxidants such as nitric acid, to form the corre- Surprisingly it has been found that, when the catalysts sponding acids. It is not possible, however, to produce according to the invention are used, the transformation a,u-dialkyl-' -cyanobutyric acids by the oxidation of the rates can be improved considerably over the processes corresponding a,ot-dialkyh'y-cyanobutyraldehydes with known hitherto. The process also has the advantage that nitric acid, because in this case the nitrile group is simulthe u-ot-dialkyl-'y-cyanobutyric acids, which are solid in taileously hydrolyzed and accordingly the dicarboxylic the normal state, are obtained directly in crystalline form. acids are obtained (Houben-Weyl, Methoden der or- The process of the invention will now be further exganischen Chemie, vol. 8, 4th ed., p. 413). The oxidation plained with the aid of examples, the results of which are of a,ot-dialkyl-y-cyanobutyraldehydes with oxygen in an summarized in the following table.

P o d t T i Expcri- Oxi- (atmos gl i e fg Temp. fii r i e l l l i l merit Compound dant Catalyst Solvent. overp su C) 111%) P 1 R =OH,R =oH o 1 B OCH 10 30-40 6 68.5 2. Some as abt lvouifl- 022 1% rhoonfli. 15-20 -50 6 60.3 3.. .-do Oz 0.5% Ti(OC H 10 30-40 6 62.8 4. Ri=C2H5, R2=C2H5 0 0.5% B(OC2H5)3 10 30-40 6 70.3 5.. l= 2H5, R==o.Ht.. 02 2.5% B(OC4H9)3 o 15-20 40-50 6 58.6 6.. RI=CH3, R2=CH3. O2 1% B(OC2H5)3 a,wdimethyl-y-cyanobutyric acid. 10 30-40 6 66. 1 7 Same as above O2 1% Ag O do 10 30-40 6 39. 2

acid or neutral medium, which is catalyzed by silver oxide and salts of silver, nickel, manganese or cobalt, and by other catalysts, does produce a,a-dialkyl-ycyanobutyric acids, but the transformation rates remain relatively unsatisfactory. In an alkaline medium the transformation rates improve, but in this case the disadvantage is that the acids are obtained in the form of their salts and first have to be set free by acidification.

The oxidation was carried out in an autoclave having a magnetic stirrer. The isolation of the reaction products is described in Examples 1, 4 and 5.

(1) Isolation of a,ot-dimethyl-y-cyanobutyric acid After the oxygen oxidation is completed, the pressure in the autoclave is relieved and the autoclave is emptied into a distillation flask in which the mixture is briefly heated in a current of nitrogen and then the unreacted a,a-dimethyl-'y-cyanobutyraldehyde is removed by distillation in vacuo at 0.2 torr between 65 and 70 C. After a small amount of first runnings, a,a-dimethyl-'y-cyanobutyric acid distills out at 124 to 126 C. and 0.1 torr and hardens crystallinely in the receiver. M.P. 48 C. (from ethyl alcohol). Transformation 68.5%

Calculated for C H NO (mol. wt. 141) (percent): C, 59.61; H, 7.81; N, 9.94. Found (percent): C, 59.66; H, 7.96; N, 10.63.

(2) Isolation of a,a-diethyl-y-cyanobutyric acid After the absorption of oxygen ends the pressure in the autoclave is relieved, and its contents are emptied into a distillation flask and the n-hexane is removed by distillation under normal pressure, under flowing nitrogen. The distillation is ended at a sump temperature of 90 C. Upon cooling, the a,u-diethyl-v-cyanobutyric acid precipitates and is removed by filtration; after recrystallizat-ion from n-heptane it has a melting point of 89 C. Transformation: 70.3%

(3) Isolation of u-ethyl-a-butyl-y-cyanobutyric acid After the oxidation With oxygen has been completed, the pressure in the autoclave is let ofl? and the autoclave is emptied into a distillation flask; the mixture is briefly heated under a stream of nitrogen and then fractionated. The a-ethyl-u-butyl-y-cyanobutyric acid boils as a single fraction at 155160 C. and 0.2 torr. Transformation: 58.6.

Calculated for C H O N (197) (percent): C, .,66.99; H, 9.64; N, 7.11. Found (percent): C, 66.59; H, 9.35; N, 7.45.

Experiment 7 was performed under the same conditions as Experiment 6 except that silver oxide was used as the catalyst instead of the ester of boric acid.

The process of this invention can be carried out batchwise or continuously as desired. It is possible to produce several batches of product and then to purify such cumulatively.

What is claimed is:

1. In the process of producing :,oc-d i-1OW61 alkylcyanobutyric acids from their corresponding aldehydes by oxidation thereof with oxygen at a temperature of about 10 to ,+200 C. at normal up to elevated pressures in the presence of a catalyst and an inert solvent; the improvement which comprises utilizing as the catalyst about 0.1 to 10 weight percent, based upon the weight of the aldehyde being oxidized of at least one member selected from the group consisting of boric and titanic acid esters having as the alcoholic moieties thereof alkyl group having up to about 6 carbon atoms.

2. The process claimed in claim 1 wherein said inert solvent is selected from the group consisting of hydrocarbons and carboxylic acids.

3. The process claimed in claim 1 carried out at about 20 to C.

4. The process claimed in claim 1 wherein the alcohol moiety of said esters is at least one member selected from the group consisting of methyl, ethyl, propyl and butyl.

5. The process claimed in claim 1 wherein the alkyl moiety of said aldehyde reactant is at least one member selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl and hexyl.

6. The process claimed in claim 2 wherein said solvent is the acid being produced.

7. The process claimed in claim 2 wherein said hydrocarbon contains no non-benzenoid unsaturation.

8. The process claimed in claim 2 wherein said solvent is at least one selected from the group consisting of benzene, toluene, xylene, cyclohex'ane, hexane, heptane, acetic acid and butyric acid.

References Cited UNITED STATES PATENTS 3,297,736 1/1967 Sohmitt et a1. 260*465.8X 3,297,740 1/l967 Schmit-t et a1. 260465.8X 3,297,741 1/1967 Schrnitt et a1. 260465.8X

JOSEPH P. BRUST, Primary Examiner U.S. Cl. X.'R. 

